Six firms are vying to advise Quincy in its quest to restart downtown redevelopment.

The consultants submitted bids to the city by Thursday’s deadline. Among the bidders were RKG Associates of Dover, N.H., a former financial adviser for Quincy’s downtown plans, and Redgate Real Estate Advisors of Boston, which led planning for the soon-to-be-built 352-unit luxury apartment complex in Marina Bay.

“These are some of the most well-known, well-respected and qualified firms in this field – not only in the greater Boston area, but nationally,” Christopher Walker, a spokesman for Quincy Mayor Thomas Koch, said.

Walker said the companies’ bid proposals, including their fees for service, legally can’t be released to the public until the mayor hires a firm. He expects Koch to make a decision soon.

Walker said the consultant hired by Koch will advise the city on how to frame the next plan for Quincy Center, in terms of project phasing and signing land deals involving the city-owned Ross Garage and Hancock Lot.

In March, Koch cut ties with Street-Works, the city’s master developer that was proposing a $1.6 billion overhaul of Quincy Center, after the New York-based firm failed to meet key project benchmarks. The mayor said Street-Works, involved in downtown planning for nearly a decade, didn’t have the financing to execute its grand plan for revitalization.

Last June, the city and Street-Works hosted a groundbreaking ceremony to celebrate the start of the project, expected to bring 3.5 million square feet of new residential, retail, office, entertainment and educational space to at least 12 Quincy Center blocks. But construction came to a halt in October, leaving a gaping hole in the ground off Chestnut Street.

In February, Quincy Mutual Fire Insurance, one of two major investors behind the first phase of the project, a block called Merchants Row, said it would no longer back Street-Works because its plans weren’t financially viable for investors.

Soon after, Koch put Street-Works on notice, saying it had a month to meet key financial benchmarks in the plan. After Street-Works failed to do so, Koch nullified the 2010 land-disposition agreement between the city and developer, which legally governed the project.

Koch has said he’ll likely re-tackle downtown redevelopment on a block-by-block basis with multiple developers, rather than partnering with one master developer.

Meanwhile, Quincy Mutual has said developer Twining Properties of New York will oversee Merchants Row as a privately-run project. Construction of Merchants Row, expected to bring new retail and residential space to Cottage Avenue, Chestnut Street and the 1400 block of Hancock Street, won’t start until spring 2015 at the earliest.

Patrick Ronan may be reached at pronan@ledger.com or follow him on Twitter @PRonan_Ledger.